Decreasing cost is required in many fields such as a field in which Wick plates used in construction equipment and bridges, etc. are welded, and a field in which thin plates used in an automobile are welded. Therefore, a tandem GMA welding method which can weld with a high efficiency has been used.
The tandem GMA welding is a method in which two welding wires used as electrodes are used, and two arcs are generated at the same time to weld. The main advantages of the tandem GMA welding are that the welding speed can be increased and the deposition rate per one weld pass can be increased.
However, since an attractive force between the two arcs is generated, a shape of a droplet is not fixed and here is a tendency for the separation properties of the droplet to be inferior. Therefore, a larger amount of the spatter is generated compared with a conventional GMA welding method using one welding wire. A great deal of time is necessary to remove the spatter attached on weld beads, and there is a problem of an increase of welding cost.
Japanese Unexamined Patent Application, First Publication No. 2003-53545 discloses a tandem GMA welding method using a solid wire for welding which is not copper-plated.
According to the Patent Document, it is reported that when a welding using a solid wire for welding, which is not copper-plated, and an inert gas-enriched shielding gas is used under fixed conditions, the amount of the spatter generated is little, stability of a molten pool is improved, and a weld bead having an excellent shape is obtained.
In addition, a mixed gas (the mixing ratio of argon is in a range of from 55 to 96%) of argon and carbon dioxide, and a mixed gas (the mixing ratio of argon is in a range of from 55 to 96%) obtained by adding oxygen or carbon dioxide into a mixed gas of argon and helium are disclosed.
[Patent Document No. 1] Japanese Unexamined Patent Application, First Publication No. 2003-53545